The present invention relates to multimedia computer speaker systems connectable to audio system control circuits (e.g., xe2x80x9csound cardsxe2x80x9d) of multimedia computers and, in particular, to such a system that employs a xe2x80x9cbridge-coupledxe2x80x9d subwoofer to reduce the number of amplifiers in the system.
Speaker systems with integral amplification electronics provide simple, compact audio reproducers for multimedia personal computers. These speaker systems, sometimes referred to as multimedia computer speaker systems, typically include pairs of wide-band speakers mounted in separate housings with amplification electronics incorporated into one or both housings. Because compactness is desirable, small, wide-band speakers (e.g., 3-inch diameter cone speaker drivers) are commonly used.
Many conventional multimedia computer systems include two-channel (stereo) multimedia computer speaker systems. Typically, a conventional two-channel computer audio system includes a two-channel audio system control circuit, which is commonly configured as a separate computer expansion board called a xe2x80x9csound card,xe2x80x9d and two wide-band audio transducers or speakers. A sub-woofer audio transducer or speaker is also included in many implementations. Conventional two-channel speaker systems are configured to provide at the two wide-band speakers distinct audio playback according to two distinct audio channels included in a multimedia computer work such as a game, music, etc. Playback at the subwoofer is typically a summed combination of the two distinct audio channels.
Typically, the speaker system includes a pair of amplifiers that provide. amplified right and left audio signals to corresponding ones of the wide-band. speakers. The subwoofer receives an audio signal that typically is generated from the right and left audio channels. In particular, the left and right audio channels are summed, and the sum is passed through a low pass filter to a sub-woofer amplifier. The subwoofer amplifier is coupled to the sub-woofer and drives it with a sum of the low-frequency components of the right and left audio channels.
Subwoofers are desirable because of the richer and deeper sounds that they provide in comparison to most two-piece multimedia computer speaker systems. However, a conventional subwoofer is a relatively expensive component of such a system due to the significant cost of the amplifier required for the subwoofer. It would be desired, therefore, to provide a three-piece multimedia computer speaker system that avoids the significant expense of conventional systems.
Accordingly, the present invention provides a multimedia computer speaker system with a pair of amplifiers that provide amplified right, and left audio signals to a pair of wide-band speakers. The amplifiers are configured to provide the amplified right and left audio signals that are out of phase with each other. The amplified right and left audio signals are applied to opposite terminals of the two wide-band speakers. For example, one signal is applied to the positive terminal of one wide-band speaker, and the other signal is applied to the negative terminal of the other wide-band speaker. These reversed terminal couplings to the wide-band speakers of the phase-reversed signals provide phase-aligned right and left audio playback at the wideband speakers.
A subwoofer is connected as a bridge-tied load to receive the amplified right and left audio signals. The phase of one amplified audio signal is in effect reversed by applying it to the negative terminal of the subwoofer. In one implementation, the right and left audio signals delivered to the subwoofer are electrically low-pass filtered. As a result, low frequency components of the phase reversed amplified audio signal are summed by the subwoofer with low frequency components of the other amplified audio signal to provide a low frequency audio playback. In another implementation, the subwoofer is contained within a ported enclosure that functions as an acoustic low pass filter. As a result, the phase-reversed audio signals are summed by the subwoofer to provide audio playback that is acoustically low-pass filtered.
The speaker system of the present invention utilizes only two amplifiers to drive three audio speakers: two wide-band speakers and a subwoofer. This speaker system employs fewer amplifiers than are used in conventional multimedia computer speaker systems. Such a reduction in electronic componentry can be significant for generally low-cost consumer articles such as multimedia computer speaker systems. The configuration of single ended amplifiers for the wideband speakers and the bridge coupled subwoofer delivers more power to the subwoofer than to the wideband speakers. The higher power demands of bass frequency audio playback are met with this configuration.
Additional objects and advantages of the present invention will be apparent from the detailed description of the preferred embodiment thereof, which proceeds with reference to the accompanying drawings.